1. Technical Field
The present invention relates to metalorganic chemical vapor deposition reactors, and more specifically, to metalorganic chemical vapor deposition reactors for producing nitride semiconductor films.
2. Description of the Related Art
Metalorganic chemical vapor deposition (MOCVD), one technique representative of vapor-phase deposition, is a method of vaporizing, for example, a Group-III organometallic compound, and, on the surface of a substrate, thermally decomposing the vaporized Group-III compound and reacting the decomposition products with a Group-V gas to deposit a film on the substrate. Because film thickness and composition can be controlled with MOCVD, and because the technique excels in terms of productivity, it is widely employed as a film-growth technology in the manufacture of semiconductor devices.
MOCVD reactors employed in MOCVD are provided with a chamber, with a susceptor disposed in the chamber, and with a channel for feeding reaction gases to the surface of substrates. In the MOCVD reactors, film deposition is carried out by placing substrates on the susceptor to heat them to an appropriate temperature, and by flowing organometallic gases through the channel to the surface of the substrates. In the film deposition, uniformizing deposited films in thickness demands from the MOCVD reactors that the reaction gas flow uniformly along the substrate surfaces. In order to flow the reaction gases uniformly along the substrate surfaces in MOCVD reactors, various channel forms have been proposed.
As a conventional MOCVD reactor, for example, Japanese Unexamined Pat. App. Pub. No. H02-291113 (Patent Document 1) discloses a vapor-phase growth system having a conduit for introducing a reaction gas to space over a substrate. The conduit has: a sample-loading room internally housing a susceptor; a constricted part whose cross-sectional form is flattened, extending along the widthwise direction of the substrate, and being short in height-wise direction of the substrate, for ejecting reaction gas over the substrate from along the substrate sideways; and guide parts positioned over the substrate, in the constricted part at intervals approximately equal to the height-wise width, or at intervals that narrow heading toward the downstream end of the reaction gas, the guide parts covering the substrates evenly from above and guiding the reaction gas along the substrate surface. The susceptor is anchored in the sample-loading room, and carries the substrate at the downstream end of the reaction-gas flow.
Furthermore, for example, Japanese Unexamined Pat. App. Pub. No. H06-216030 (Patent Document 2) discloses a compound semiconductor vapor-phase growth system having a flow channel for introducing a reaction gas onto a substrate. The flow channel is tapered such that the height-wise width narrows from the upstream end of the flow channel gradually toward the downstream end of the flow channel. A susceptor is anchored under where the flow channel is tapered.
Moreover, Japanese Unexamined Pat. App. Pub. No. H2-291114 (Patent Document 3) and Japanese Unexamined Pat. App. Pub. No. H2-291113 (Patent Document 1) disclose a vapor-phase growth system provided with a rotating susceptor for carrying a substrate, and with a linear line for introducing a reaction gas to the substrate. The liner line monotonically diminishes in height over the reaction gas conduit.
Improving film-deposition efficiency is being demanded from MOCVD reactors. Scaling up the susceptor makes it possible to heat many substrates at once, and to grow films onto substrates of large diametric span, leading to the improvement of film-deposition efficiency. Scaling up the susceptor, however, enlarges the distance between the upstream and downstream ends of the susceptor, leading to a significant difference between reaction gas conditions (for example, concentration and temperature of the reaction gas) on the upstream and downstream ends of the susceptor. As a result, the thickness of the deposited films proves to be non-uniform. For this reason, to date, improving film-deposition efficiency while the films to be deposited are uniformized in thickness has not been realized.